1. Field of Invention
This invention relates to a microwave deicing and anti-icing system for aircraft wings, rotors, and airfoils utilizing thermal energy transformed from microwave radiation.
2. Description of the Related Art
Deicing of aircraft wings, rotors, airfoils and other equipment is essential for all-weather winter operation when flying in meteorological conditions where ice accumulation adversely affects lift, drag, weight and otherwise decreases a vehicle's performance.
Typically, turbojet aircraft rely upon heated, high-pressure air to prevent ice buildup on structural wing sections. This bleed air is normally tapped from the turbojet engine at a cost in fuel and decreased thrust as well as increased weight due to extensive, heavy steel ducting systems and associated valves and control mechanisms.
Turboprop aircraft seldom use heated high pressure bleed air for this purpose since they can't afford the performance decrements and weight of such systems. They more commonly employ the 1920's technology of pneumatic deicer boots which inflated in order to break a thin layer of ice that is allowed to accumulate on the wings so that it will be carried away by the slipstream. This system is inefficient and can be fatal as is evidenced by recent tragic losses of turboprop commuter aircraft in October and December of 1994. Other deicing and anti-icing systems include electrically heated pads and electrical vibrating devices. None of these has been used to any extent other than experimentation and military applications due to high costs, high electrical energy requirements, and excessive weight.
In previous microwave deicing and anti-icing systems, as portrayed in U.S. Pat. Nos. 4,060,212, 4,365,131 and 5,061,836, microwave energy is used to prevent icing by directing microwave energy transmitted directly or through a dielectric surface waveguide to the ice or super-cooled water droplets in front of the wings or to remove ice from propulsion blades by treating radially inward surfaces of the blades. The energy loss can be great when microwave is transmitted through the air. Only a small fraction of the transmitted microwave is intercepted by the surfaces which need to be deiced because the microwave is emitted at all angles. Also, because of the reflection of microwave energy from the surface to be deiced, further loss of microwave energy is expected. A dielectric surface waveguide is better in this respect, but it complicates the manufacturing procedures. Therefore the transmission of microwave energy by methods of the prior art is too inefficient to warrant its practical use.